Preprints
https://doi.org/10.5194/egusphere-2023-1342
https://doi.org/10.5194/egusphere-2023-1342
09 Aug 2023
 | 09 Aug 2023

Evaluating marine dust records as templates for optical dating of Oldest Ice

Jessica Ng, Jeffrey Severinghaus, Ryan Bay, and Delia Tosi

Abstract. The continuous ice core record extends 800,000 years into the past, covering the period of 100,000-year glacial cycles, but not the transition from 40,000-year glacial cycles (the Mid-Pleistocene Transition, 1.2–0.7 million years ago). A primary goal of the International Partnership in Ice Core Sciences is therefore to retrieve a 1.5-million-year-old continuous ice core, increasing our understanding of this major change in the climate system and thus of fundamental climate forcings and feedbacks. However, complex glacial processes, limited bedrock data, and surprisingly young basal ice in previous cores necessitate careful reconnaissance studies before extracting a full core.

Ice borehole optical logging reflects the ice dust content and may be used to date ice quickly and inexpensively if a reference record is known. Here we explore the relationship between ice dust records and well-dated marine dust records from sediment cores in the southern Atlantic and Pacific Oceans, which lie along paths of dust sources to Antarctica. We evaluate how representative these records are of Antarctic dust both through the existing ice core record and during the older target age range, suggesting that a newly published 1.5 million year record from site U1537 near South America is likely the most robust predictor of the Oldest Ice dust signal. We then assess procedures for rapid dating of potential Oldest Ice sites, noting that the ability to detect dating errors is an essential feature. We emphasize that ongoing efforts to identify, recover, date, and interpret an Oldest Ice core should use care to avoid unfounded assumptions about the 40 kyr world based on the 100 kyr world.

Jessica Ng, Jeffrey Severinghaus, Ryan Bay, and Delia Tosi

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1342', Eric Wolff, 15 Aug 2023
  • RC2: 'Comment on egusphere-2023-1342', Frédéric Parrenin, 23 Aug 2023
  • RC3: 'Comment on egusphere-2023-1342', Lorraine Lisiecki, 02 Oct 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1342', Eric Wolff, 15 Aug 2023
  • RC2: 'Comment on egusphere-2023-1342', Frédéric Parrenin, 23 Aug 2023
  • RC3: 'Comment on egusphere-2023-1342', Lorraine Lisiecki, 02 Oct 2023
Jessica Ng, Jeffrey Severinghaus, Ryan Bay, and Delia Tosi
Jessica Ng, Jeffrey Severinghaus, Ryan Bay, and Delia Tosi

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Short summary
The pattern of Earth’s ice age cycles shifted around a million years ago, becoming more extreme and longer in duration. Multiple projects are underway to obtain an Antarctic ice core that covers this time period, as ice cores contain important clues to why the transition happened. To make sure the ice is old enough at the bottom, we demonstrate how to use new technology to quickly measure dust patterns in the ice and compare them to dust in deep ocean sediments whose ages are known.